This invention relates in general to the construction of solar cells and in particular to a new and useful solar cell based on CuInS.sub.2 and a method for producing such cells.
The invention relates to solar cells with a photoanode based on CuInS.sub.2 semiconductor material, as well as a method for their production.
From U.S. Pat. No. 4,601,960 issued Dec. 17, 1985 and Canadian patent application Ser. No. 460,597 filed Aug. 9, 1984 it is known to employ, for photoelectrochemical solar cells, a working electrode which is constructed with a semiconductor layer which consists of a ternary compound of the material systems CuInSe.sub.2 or CuInS.sub.2, including the homogeneity ranges and in-situ produced surface modifications of these compounds. However, detailed information is found in this known prior art only with respect to CuInSe.sub.2 material.
In connection with more advanced work in this field, it has been found, surprisingly, that a material based on CuInS.sub.2, in contrast to high-purity CuInSe.sub.2 material, wherein extraneous phases are admitted in a controlled manner, leads to a still higher efficiency, namely about 12.5%, for the transformation of light energy into electrical energy.
It has also been known for some years how to construct solar cells from semiconductor hetero-compounds (for example: Thin Solid Films Vol. 102 (1983), Electronics and Optics, pages 1 to 46, in particular pages 33 and 34). This involves the use of pairs of structures consisting of a transparent semiconducting metal oxide with a large energy gap and an active semiconductor with a lower bandgap, i.e. structures of the SIS type (semiconductor/insulator/semiconductor).
Until now, silicon was especially widely used as an active semiconductor material. More recently, efforts have been made to use other materials for solid state solar cells.
As for a photoelectrochemical solar cell, structural details can be found in the above-mentioned U.S. Pat. No. 4,601,960.